Jar Test
Adjust the pH
of your diluted nutrient solution to your target pH of 6.5, 7.0 etc.,
and place about 200 ml in a clean, clear glass container. Stir the
contents as often as possible over a 1 hour period. Then, immediately
after briefly stirring, place the glass in front of a bright light and
closely examine the contents. The presence of fine white particles or
flocculent/gelatinous particles verifies that precipitation has
occurred and that that pH value is too high for optimal results (see
"stirred" bottle in Fig 1.2b). If uncertain
of the results, cover the glass with a piece of paper and allow the
mixture to stand for 24 hours. Any precipitate will then be evident by
the presence of a white deposit either floating on the surface or on
the bottom of the container (see "unstirred" bottle in the above
picture).
Notes:
a) The stirring
over the 1 hour period simulates the water movement in an NFT system
and accelerates the rate of precipitation.
b) The stirring
prior to the visual examination is to ensure that all particles lift
up from the base of the glass and into the viewing zone for easier
detection. Also, it is much easier to detect the presence of small
particles when they are moving.